It is known to provide synthetic resin foil webs, i.e., so-called plastic mulches, for use as a ground covering in regions in which vegetation growth is to be prevented or limited. For example, desired plants may be grown through holes which then serves primarily to prevent the growth of weeds from detracting from the desired plant growth.
Such mulches and ground covers are also provided beneath decks or other structures in regions which are to be maintained free from vegetation and along landscape areas in which the growth of vegetation is to be prevented permanently or for a limited period of time to enhance a landscaping effect for example.
These mulches have been used for many years for this purpose and generally consist of a black plastic, e.g. a polyurethane or preferably high density polyethylene.
Synthetic resin foils for this purpose can have a thickness of 80 micrometers or more and a web width of, say, 1 meter.
A particularly advantageous use of such growth-preventing strips is along highways and roadways, for example, below median barriers and elsewhere where vegetation growth is undesired.
The barriers can be supported on posts at intervals of 4 meters, for example, and the strips must clear such posts.
Because the synthetic resin foils which have been used tend to be picked up by the wind and displaced, it has been a common practice to weight the strips down by stones or the like which may be randomly placed on the strips.
Not withstanding the fact that this approach can generally serve to hold the strips in place, existing plastic mulches and growth-preventing plastic strips have the drawback that with time the foil deteriorates by the effect of sunlight and especially the ultraviolet component of sunlight.
Furthermore, the wind, especially a strong wind, can act upon the foil strip between the individual stones which serve to hold the strip in place and in combination with the weakening of the foil by ultraviolet light, the wind can damage the foil, i.e. can tear the foil so that the antivegetation effect will be lost.
The ultraviolet effect on the foil appears to be an accelerated oxidation of the polymer which results in a rupture of the molecular chains. With such deterioration of the foil, of course, the antivegetation effect can be lost even if there is little or no wind damage.
By and large, therefore, such plastic strips for preventing the growth of vegetation have proved incapable of tolerating long periods of exposure to sunlight, high winds or a combination of the two and have had in the past a relatively short useful life.